Lubricating oil of improved high temperature properties



United States Patent 3,128,246 LUBRECATING 01L (BF HMPROVED HEGH TEMPERATURE PROPERTTEEi Edward A. fiber-right, Woodhury, and Robert H. Williams,

Pennington, NJ., assignors to Socony Mobil Oil Company, Inc., a corporation of New York No Drawing. Filed Sept. 14, 1%0, Ser. No. 55,825

4 Claims. ((31. 208-255) This invention relates to petroleum oils and particularly to petroleum lubricating oils of enhanced high temperature properties.

As is well known, petroleum lubricating oils tend to deteriorate or partially decompose and oxidize when subjected to high temperatures. This deterioration is evidenced by the deposition of adhesive deposits on the hot metal surfaces with which the lubricating oil comes in contact. During use in an internal combustion engine, for example, due to the high temperatures, i.e., 400 F. to 650 F., encountered in the piston ring zone, the oil oxidizes and forms lacquer-type deposits in and around the piston rings. The accumulation of these deposits causes the rings to malfunction, i.e., they tend to stick. There is a loss of power as the rings fail to hold the combustion gases in the combustion chamber. Stuck oil rings result in poor lubrication of the moving piston. Some oil always works its way into the combustion chamber where it oxidizes to carbonaceous deposits which raise the compression ratio of the engine. Engines in such condition require gasolines of high octane number to operate without knocking. These deposits also lead to pre-ignition, i.e., ignition of the fuel charge before spark-ignition takes place.

Heretofore, it has been sought to overcome the lacquerforming tendencies of oil subjected to high temperatures by the addition to the oil of various stabilizing agents. Experience has shown, however, that although these stabilizing agents are usually efliective for increasing the stability of the oil at temperatures up to about 300 F. they have generally been ineffective at higher temperature levels, i.e., from 400 F. to 650 F., to which the oil is subjected when in use in an engine.

In accordance with the present invention, a way has been found to markedly reduce the lacquer-forming tendencies of an oil under the latter high temperature conditions without the use of stabilizing agents. It is, therefore, the primary object of this invention to provide a novel and economicallyfeasible means for improving lubricating oils with respect to their high temperature lacquer-forming tendencies. Further objects of the invention will be apparent from the following description.

In accordance with the invention, it has been found that by treating the oil with from about 5% to about 25%, by weight, preferably about to by weight, of an organic peroxide, such as di-tertiary-butyl peroxide, for a period of from about one to about hours, at a temperature ranging from about 100 C. to about 200 C., the type of deposit laid down by the oil when it is oxidized at high temperatures, such as encountered by the oil in use in an engine, are changed from adhesive, lacquer-type deposits to light powdery deposits which are readily removed from the metal surfaces. This type of deposit, therefore, will not build up on the piston rings, and when formed in the combustion chamber will be immediately blown out through the exhaust valve opening.

Besides improving the type of deposit formed by the oil when subjected to high temperatures, the peroxide treatment raises the viscosity of the oil. This is an added advantage of the treatment in that hydrocarbon oils having initial viscosities below the lubricating range can be raised in viscosity to the lubricating range. The treat- 3,128,246 Patented Apr. 7, 1964 ment also improves the viscosity index of the oil in most cases, which, of course, is a highly desirable effect.

The following specific examples and tests will serve to fully illustrate the invention.

EXAMPLE I A mixture of 150 grams of a solvent-refined Mid-continent distillate oil and 15 grams (10% by weight) of di-t-butyl peroxide were reacted under reflux at 130 C. to 150 C. for 9 hours. During the reaction, t-butyl alcohol was formed which was removed by distillation. The treated oil amounted to 150 grams or yield. The viscosity properties of the treated and untreated oils are shown in Table I.

Table I K.V. K.V. 100 F 210 F. V.I.

in es. in cs.

Untreated oil 43. 84 6. 21 96 Treated oil 97. 46 10. 58 99 EXAMPLE II A mixture of 822 grams of a solvent-refined Kuwait distillate oil and 117 grams (14.3% by weight) of di-tbutyl peroxide was heated for 12 hours at 120 C. to C. and the t-butyl alcohol that formed was removed by distillation. 810 grams of treated oil was then given a second treat with 100 grams (12% by weight) of di-tbutyl peroxide at 120 C. to 150 C. for 8 hours. The alcohol formed was removed as before. The viscosity properties of the treated and untreated oils are shown in Table Ii.

A mixture of 185.0 grams of a solvent-refined East Texas distillate oil and 14.6 grams (8% by weight) of dit-butyl peroxide were reacted under reflux for about 12 hours at a temperature of 125 C. to C. Unreacted peroxide and t-butyl alcohol were removed by vacuum distillation in a stream of nitrogen at C. for one hour. The oil recovered weighed essentially the same as the oil charged. The viscosity characteristics of the treated and untreated oils are shown in Table III.

Table III K.V. K.V.

100 F 210 F. V.I.

in es. in cs.

Untreated oil 31. 54 5. 17 103 Treated Oil 43. 21 6.37 106 The untreated oil and the treated oil were separated into aromatic and non-aromatic fractions by percolation over silica gel. The physical properties of these separated fractions are shown in Table IV. It will be seen that most of the change took place in the aromatic fraction. Since it is generally recognized in the art that the aromatic portion of a lubricating oil contributes most to engine deposits, it is believed that the reduced lacquerforming tendencies of the treated oils is due primarily to the changes eifected in the aromatic fraction.

EXAMPLE IV A mixture of 185 grams of a solvent-refined East Texas distillate oil and 14.6 grams (8% by weight) of di-t-butyl peroxide were reacted under reflux for about hours at a temperature of 131 C. to 151 C. The reaction mass was subjected to distillation at atmospheric pressure and at a maximum liquid temperature of 160 C., whereby 6.2 ml. (5.5 grams) of distillate were recovered. Of this, 1.1 ml. proved to be unreacted di-tbutyl peroxide and 5.1 ml. was t-butyl alcohol. Then 5.5 grams of di-t-butyl peroxide were added back to the reaction mixture and the reaction continued for another 9 /2 hours between 125 C. and 156 C. The unreacted peroxide and the t-butyl alcohol were removed by topping to 170 C. in a stream of nitrogen under vacuum. The weight of oil recovered was essentially the same as that charged. The properties of the untreated and treated HIGH TEMPERATURE OXIDATION TEST To demonstrate the effectiveness of the peroxide treatment of the invention in overcoming the lacquer-forming tendencies of the oil, the treated and untreated oils were compared in a high temperature oxygen absorption test unit. In this test the oil is fed to the center of a rotating heated disc. The rotation of the disc (2500 rpm.) spreads the oil in a thin film over the disc. As the oil is thrown from the disc it is cooled by a circular condenser. Air is pumped over the thin oil film and as oxygen in the air reacts with the oil, make-up oxygen is automatically supplied from a gas burette reservoir. By reading the gas burette every 5 minutes the rate of oxygen absorbed per 5 minutes is determined. This is the oxidation rate; the larger the number the less stable the oil. The oil is recycled over the hot rotor 12 times. At the end of the test the deposit remaining on the rotor after wiping is rated visually, similar to that used in rating pistons of engines. A rating of 100 indicates a perfectly clean disc while a rating of 0 means that the disc is completely covered by a heavy black lacquer. The test results are given in Table VI. It is seen from the test results that, compared at the same temperature levels, the treated oil in all instances was superior to the untreated oil from the standpoint of the amount of lacquer-type deposit formed, even though in one instance (Example I) the oxidation rate was somewhat higher for the treated oil. Furthermore, it is seen that the improvement effected in the treated oil over the untreated oil actually increases with increase in temperature. Thus, the treated oil of Example II (i.e., Example II-B) gave a cleaner disc at 575 F. than the untreated oil at 500 F.

Table VI HIGH TEMPERATURE OXIDATION TEST Oxidation Cleanliness Oil Tempera- Rate, Rating ture, F. ce/5 Min. After 12 Cycles Untreated oil of Example I 550 101 83 Treated oil of Example I 550 112 94 Untreated oil of Example II 500 23 88 525 45 79 550 110 68 575 314 9 Treated oil of Example II-B 525 39 94 550 73 94 575 147 94 600 186 57 Although di-tertiary-butyl peroxide is preferred for use in the invention, it will be apparent to those skilled in the art that other organic peroxides may also be used. Thus, peroxides, such as benzoyl peroxide, acetyl peroxide, tertiary-butyl hydroperoxide, 1,1-dimethyl propyl peroxide, l-methyLl-ethyl butyl peroxide, etc., though somewhat less effective than di-tertiary-butyl peroxide, may be advantageously employed.

The lubricating oils treated in accordance with the invention may, of course, contain one or more additives designed to improve the various characteristics thereof, such as detergents, extreme pressure agents, pour point depressants, anti-rust agents, non-foaming agents, etc. Furthermore, although the treatment of the oil in accordance with the invention improves the oil from the standpoint of the type of deposit formed under high temperature conditions and also generally improves the viscosity index thereof, it will be appreciated that it may be desirable in some cases to further improve the oil by the addition of an antioxidant or a viscosity index-improving agent.

Although the principle of this invention has been described and illustrated herein by means of certain specific examples and embodiments thereof, it is not intended that the scope of the invention be limited in any way thereby, but only as indicated in the following claims.

We claim:

1. The method of treating a conventionally refined petroleum lubricating oil to reduce its tendency to form lacquer-type deposits under high temperature conditions which comprises treating said oil with from about 5% to about 25 by weight, of an organic peroxide at a temperature of from about C. to about 200 C. for a period of from about one to about 20 hours and distilling oif alcohol formed in the course of said treatment and unreacted peroxide.

2. The method of treating a conventionally refined petroleum lubricating oil to reduce its tendency to form lacquer-type deposits under high temperature conditions which comprises treating said oil with from about 5% to about 25%, by weight, of di-tertiary-butyl peroxide at a temperature of from about 100 C. to about 200 C. for a period of from about one to about 20 hours and distilling off di-tertiary-butyl alcohol formed in the course of said treatment and unreacted di-tertiary-butyl peroxide.

3. The product obtained by the method of claim 1.

4. The product obtained by the method of claim 2.

References Cited in the file of this patent UNITED STATES PATENTS 2,726,194 Van Beest et a1. Dec. 6, 1955 2,749,284 Noble June 5, 1956 2,782,143 Bicke Feb. 17, 1957 2,934,487 Whitney Apr. 26, 1960 2,955,084 Bartleson et a1. Oct. 4, 1960 

1. THE METHOD OF TREATING A CONVENTIONALLY REFINED PETROLEUM LUBRICATING OIL TO REDUCE ITS TENDENCY TO FORM LACQUER-TYPE DEPOSITS UNDER HIGH TEMPERATURE CONDITIONS WHICH COMPRISES TREATING SAID OIL WITH FROM ABOUT 5% TO ABOUT 25%, BY WEIGHT, OF AN ORGANIC PEROXIDE AT A TEMPERATURE OF FROM ABOUT 100*C. TO ABOUT 200*C. FOR A PERIOD OF FROM ABOUT ONE TO ABOUT 20 HOURS AND DISTILLING OFF ALCOHOL FORMED IN THE COURSE OF SAID TREATMENT AND UNREACTED PEROXIDE. 